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Date:   Thu, 10 Dec 2020 18:17:28 +0000
From:   Dave Martin <Dave.Martin@arm.com>
To:     "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
Cc:     Heinrich Schuchardt <xypron.glpk@gmx.de>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
        linux-man@vger.kernel.org
Subject: Re: cacheflush.2
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On Wed, Dec 09, 2020 at 07:34:09PM +0100, Alejandro Colomar (man-pages) wrote:
> Hi Heinrich & Michael,
> 
> What about the following?:
> 
> [
> NOTES
>        GCC provides a similar function, which may be useful on  archi‐
>        tectures that lack this system call:
> 
>            void __builtin___clear_cache(void *begin, void *end);
> ]
> 
> Cheers,
> 
> Alex

Maybe we should discourage people from calling the cacheflush syscall?

I think that people shouldn't be using the syscall unless they really
need the finer grained control it provides, and are prepared to take a
hit to portability.

(On arches where userspace is allowed to do cache flushing directly,
__builtin___clear_cache() should transparently do the right thing, with
no syscall overhead -- if not, that's probably a bug in the toolchain or
compiler support library.)

[...]

Cheers
---Dave